The present invention generally relates to a dielectric resonator, with an internal conductor which is formed within a dielectric, and an external conductor which is formed on the outside face of the dielectric, and a method for adjusting the characteristics of a dielectric resonator.
A dielectric resonator, where a resonator electrode is formed within a dielectric block and an earth electrode is formed on the outside face of the dielectric block, and a so-called tri-plate type of dielectric resonator with strip lines that are opposite to each other by the use of a dielectric basic plate with a strip line being formed on one main face and an earth electrode which is formed on the other main face, are used as a band passing filter and so on in, for example, the microwave band.
FIG. 39 shows as an exploded perspective view the construction of the conventional general dielectric resonator using the dielectric block. In FIG. 39, reference numeral 40 is a six-sided dielectric block with three internal conductor shaped holes 46, 47, 48 having an internal conductor provided therein and coupling holes 49, 50 which are provided among the internal conductor formed holes 46, 47, 48. The internal conductor is formed on the inside surface of the internal conductor formed holes 46, 47, 48, and an external conductor 51 is formed on five faces of the dielectric block 40 except for an open face 52. Reference numerals 53, 54 are so-called resin pins, each being composed of resin portions 53a, 54a and signal input, output terminals 53b, 54b. Two resin pins 53, 54 are inserted into the internal conductor formed holes 46, 48 from the open face side of the dielectric block 40 so that the terminals 53b, 54b are coupled in capacity to the internal conductor within the internal conductor formed holes 46, 48. Reference numeral 55 is a case for retaining the dielectric block 40 and the resin pins 53, 54 and also, for covering the open face portion of the dielectric block 40. The resin pins 53, 54 are respectively inserted into the dielectric block 40 so as to cover the case 55, and also, the whole arrangement is integrated by soldering the dielectric block 40 with the external conductor 51. In mounting the dielectric resonator, the projecting portions 55a, 55b of the case 55 function as an earth terminal.
As shown in FIG. 39, many of the components such as input, output terminals 53b, 54b, case 55 and so on, are necessary if a plurality of resonators are to be formed on a single dielectric block. The assembling steps therefore become complicated. Moreover the completed products, which have to be mounted as electronic components, require that a lead wire attached to the component be mounted in the mounting operation of the completed product on the circuit basic plate. Therefore, the surface mounting operation cannot be effected, as in other electronic components, so as to mount these completed products on the same circuit basic plate, so that a lower height operation is hard to effect. If the case 55 is not used, by the direct connection of the external conductor 51 of the dielectric block 40 to the earth electrode on the circuit basic plate, the open face 52 is exposed, and, therefore, electromagnetic field leakage is caused in this portion. When a metallic member approaches toward the open face 52, the influences of the metallic member are received. Also, the resonator is connected with electromagnetic field from the outside so that the desired characteristics of the dielectric resonator cannot be obtained.